feat(openapi): Add new features and improvements to the API specification

- Add "strict" field to "OpenAIFunction" for controlling schema adherence
- Add "description" field to "description" field in "OpenAIFunction"
- Add new "ClientInboundMessageTransfer" type for transferring calls
- Add new "StepDestination", "HandoffStep", and "AssignmentMutation" types for workflow steps
- Add new "CallbackStep" type for calling back to previous steps
- Add "slackSupportEnabled" and "slackChannelId" fields to "Subscription"
- Update "hipaaCommonPaperAgreementId" field in "Subscription"
- Update type of "time" field in "Log" from number to string
- Update available models to include "gpt-4o-2024-08-06"

Author: fern-api[bot]